Clay reinforced dual core a golf ball

ABSTRACT

A golf ball with a center core comprising polybutadiene and a clay material in an amount ranging from 0.4 to 2.5 weight percent of the center core is disclosed herein. Alternatively, the golf ball has a mantle layer with a blend of ionomer materials and a clay material in an amount ranging from 0.4 to 2.5 weight percent of the mantle layer.

CROSS REFERENCES TO RELATED APPLICATIONS

The Present Application is a divisional application of U.S. patent application Ser. No. 15/657,992, filed on Jul. 24, 2017, which claims priority to U.S. Provisional Patent Application No. 62/370,165, filed Aug. 2, 2016, each of which is hereby incorporated by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION Field of the Invention

The present invention generally relates to the use of clay in layers of a golf ball.

Description of the Related Art

Clays are typically inorganic layered silicates held together by ionic and Van der Waal interactions. If properly incorporated, clays can improve mechanical and barrier properties of composite materials. These improved benefits are observed when clays are intercalated and or exfoliated inside a polymer matrix (Lee, 1996; Yano 1997). Intercalation/exfoliation is achieved by mechanical agitation, ultra-sonication, and surface modification of clay. Surface modification is necessary to improve compatibility of clays which are hydrophilic in nature with polymers that are hydrophobic. Surface modification of clay generally includes treatment with long alkyl chain amines which replace cations in between clay layers. Replacing cations with these amines increases their compatibility with organic polymers that helps intercalate and or exfoliate clay layers. Most common amines used for surface modification of clay are 1-hexadecyl amine, 1-octadecyl amine, octadecyl triammonium bromide, benzyl butyl dimethylammonium bromide, and benzyl trimethylammonium bromide (Vaia 1996; Wang, 1996). Because of their lower cost and commercial scale availability they have recently gained popularity over other fillers. One of the first commercial examples of clay incorporation in polymer matrix was described by Toyota scientists in 1993 (Usuki 1993; Usuki, 1995). Nylon 6 and clay nanocomposite was synthesized by polymerization of caprolactam in presence of montmorillonite clay that resulted nylon composite with better mechanical properties.

The prior art fails to even recognize this problem.

BRIEF SUMMARY OF THE INVENTION

The primary purpose of the present invention is to improve durability of golf ball core by incorporation of clay in either the core or mantle layers to improve the impact strength of the ball. This benefit can be seen in either a ball with single piece core, or a dual core with an outer core firmer than the inner core. Improved durability of the core or mantle composition by using clay can result in higher mean time to fail (MTTF) upon repeated impact in a high speed testing device, or with a golf club in normal play.

Another purpose of the present invention is to improve aging properties due to the incorporation of clay in either the core or mantle layer for better retention of compression and COR over time.

Having briefly described the present invention, the above and further objects, features and advantages thereof will be recognized by those skilled in the pertinent art from the following detailed description of the invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is an exploded partial cut-away view of a golf ball.

FIG. 2 is top perspective view of a golf ball.

FIG. 3 is a cross-sectional view of a core component of a golf ball.

FIG. 4 is a cross-sectional view of a core component and a mantle component of a golf ball.

FIG. 5 is a cross-sectional view of an inner core layer, an outer core layer, an inner mantle layer, an outer mantle layer and a cover layer of a golf ball.

FIG. 5A is a cross-sectional view of an inner core layer, an intermediate core layer, an outer core layer, a mantle layer and a cover layer of a golf ball.

FIG. 6 is a cross-sectional view of an inner core layer under a 100 kilogram load.

FIG. 7 is a cross-sectional view of a core under a 100 kilogram load.

FIG. 8 is a cross-sectional view of a core component and a mantle component of a golf ball.

FIG. 9 is a cross-sectional view of a core component, the mantle component and a cover layer of a golf ball.

FIG. 10 is an exploded partial cut-away view of a four-piece golf ball.

FIG. 11 is an exploded partial cut-away view of a three-piece golf ball.

FIG. 12 is an exploded partial cut-away view of a two-piece golf ball.

FIG. 13 is a cross-sectional view of a two-piece golf ball.

FIG. 14 is a cross-sectional view of a three-piece golf ball.

FIG. 15 is an exploded partial cut-away view of a three-piece golf ball.

FIG. 16 is a cross-sectional view of a three-piece golf ball with a dual core and a cover.

FIG. 17 is a cross-sectional view of a three-piece golf ball with a core, mantle and cover.

FIG. 18 is a cross-sectional view of a four-piece golf ball with a dual core, mantle layer and a cover.

FIG. 19 is a cross-sectional view of a four-piece golf ball with a core, dual mantle layers and a cover.

FIG. 20 is a graph of durability testing of solid cores using PTM at 175 fps.

FIG. 21 is a graph of durability testing of solid cores using PTM at 150 fps.

FIG. 22 is a graph of the effect of type of clay on compression.

FIG. 23 is a graph of the effect of type of clay on COR.

FIG. 24 is a graph of the effect of type of clay on MTTF.

FIG. 25 is a graph of the durability testing of dual cores using PTM at 175 fps.

FIG. 26 is a graph of the durability testing of mantles using PTM at 175 fps.

DETAILED DESCRIPTION OF THE INVENTION

One objective of the present invention is to improve durability of golf ball core by incorporation of clay in either the core or mantle layers to improve the impact strength of the ball. This benefit can be seen in either a ball designed to have a low compression single piece core, or a dual core with an outer core firmer than the inner core. Improved durability of the core or mantle composition by using clay can result in higher mean time to fail (MTTF) upon repeated impact in a high speed testing device, or with a golf club in normal play.

Another objective of the present invention is to improve aging properties due to the incorporation of clay in either the core or mantle layer for better retention of compression and COR over time.

Nanoclay (montmorillonite type) used in this study was either modified using octadecyl amine (ODA) or a combination of both ODA and silane. Terms clay or nanoclay would be used interchangeably in this study. Clay modified with a combination of ODA and silane would be referred to as silane modified clay henceforth. Silane used for modification generally has a functional amine group and moisture curing methoxy or ethoxy groups. Some of the examples of aminosilanes that can be used for modification of clay are (3-Aminopropyl) triethoxysilane, trimethoxy[3-(methylamino)propyl]silane, and (N,N-Dimethylaminopropyl)trimethoxysilane.

Experiment/Results

Clay in Cores.

Polybutadiene based cores were made using following materials. Corresponding levels (by % wt) is mentioned next to each material.

Polybutadiene with more than 60% 1,4-cis structure-(40-90%);

Polyisoprene-(1-30%);

Zinc diacrylate-(10-50%);

Zinc oxide-(1-30%);

Zinc stearate-(1-20%);

Peroxide initiator-(0.1-10%);

Zinc pentachlorothiophenol-(0-10%);

Color-(0-10%);

Barium sulfate-(0-20%);

Clay-(0.01-6%)-available from various suppliers such as FCC Inc., Bentonite Performance Minerals LLC, Minerals Technology Inc., Byk Additives;

Clay masterbatch (a masterbatch of 90-99% polybutadiene and 1-10% clay)-(0.1-50%)-custom compounding can be done with the help of various suppliers such as Preferred Compounding Corp, Dyna-Mix, Alttran, Callway (in house compounding.

Clay in Single Piece Core-Silane modified clay.

In this study clay was added to a polybutadiene recipe in a large single core. The solid core was cured within a temperature range of 150-400 F for times ranging from 1-30 minutes. After molding, the solid cores were spherically ground to approximately 1.590″ prior to testing.

Table 1 gives details of recipe of solid core containing silane modified clay. Components from these recipes were mixed in an internal mixer. Optionally, additional mixing was done using a two roll mill.

TABLE 1 Recipe of solid core (silane modified clay) Formula Formula Formula Formula 1 2 3 4 Components % wt % wt % wt % wt Polybutadiene rubber 62.5 62.2 61.9 61.3 Polyisoprene rubber 0.0 0.0 0.0 0.0 Zinc diacrylate 19.9 19.8 19.7 19.5 Zinc oxide 6.3 6.2 6.2 6.1 Zinc stearate 3.8 3.7 3.7 3.7 Peroxide initiator 0.5 0.5 0.5 0.5 Zinc pentachlorothiophenol 0.6 0.6 0.6 0.6 Color 0.1 0.1 0.1 0.1 Barium sulfate 6.4 6.4 6.4 6.3 Silane modified clay 0.0 0.5 1.0 2.0 clay masterbatch 0.0 0.0 0.0 0.0 Properties of core Compression 68.7 70.4 69.9 71.6 COR (coefficient of 0.800 0.802 0.800 0.798 restitution @ 125 fps) Durability score or mean 39 51 71 62 time to fail MTTF (number of shots after which ball starts to crack/fail)

Compression is measured by applying a 200 pound load to the core and measuring its deflection, in inches. Compression=180−(deflection*1000).

Durability Testing of Solid Cores

Cores were shot at 150 fps in a pneumatic testing machine (PTM).

For each formula mentioned in Table 1, 12 cores were tested. Number of shots after which each core cracked was recorded for each core, and the cracked core was removed from the remainder of the test. The data was reported using a Weibull plot, and the mean time to fail was reported as shown in Table 1. As seen in FIG. 20, clay modified cores endured more shots before failure compared to cores with no clay. It is reasonable to assume that the durability of a golf ball having a single piece core of this design will also experience a dramatic increase in crack durability based on this improvement to the core.

Clay in Single Piece Core-ODA modified clay.

Cores from ODA modified clay were made as per recipe shown in Table 2. Components from these recipes were mixed in an internal mixer. Optionally, additional mixing was done using a two roll mill.

TABLE 2 Recipe of solid core (ODA modified clay) Formula Formula Formula Formula 1 2 3 4 Components % wt % wt % wt % wt Polybutadiene rubber 62.5 62.2 61.9 61.3 Polyisoprene rubber 0.0 0.0 0.0 0.0 Zinc diacrylate 19.9 19.8 19.7 19.5 Zinc oxide 6.3 6.2 6.2 6.1 Zinc stearate 3.8 3.7 3.7 3.7 Peroxide initiator 0.5 0.5 0.5 0.5 Zinc pentachlorothiophenol 0.6 0.6 0.6 0.6 Color 0.1 0.1 0.1 0.1 Barium sulfate 6.4 6.4 6.4 6.3 ODA modified clay 0.0 0.5 1.0 2.0 Clay masterbatch 0.0 0.0 0.0 0.0 Properties of core Compression 71.4 72.6 74.8 77.6 COR (coefficient of 0.801 0.800 0.798 0.792 restitution @ 125 fps) Durability score or mean 31 50 36 48 time to fail MTTF (number of shots after which ball starts to crack/fail)

As seen in FIG. 21, clay modified cores endured more shots before failure compared to cores with no clay. It is reasonable to assume that the durability of a golf ball having a single piece core of this design will also experience a dramatic increase in crack durability based on this improvement to the core.

Comparison of Silane and ODA Modified Clay

Compression, durability, and COR results of cores incorporated with silane and ODA modified clay were compared. It was found that for the same loading compared to ODA modified clay, silane modified clay resulted in lesser change in compression than control (FIG. 22).

When compared to ODA modified clay, silane modified clay maintained a higher COR for the same loading (FIG. 23).

Durability of silane modified cores was found to be better than ODA modified clay at the same clay loading (FIG. 24).

Clay in Dual Core

In this study clay was introduced to the outer core in a dual core construction. Dual cores were made by compression molding two outer core halves around an already molded inner core having a diameter of approximately 0.940″ and a soft compression of approximately 0.200 inches of deflection under a 200 lb load.

Curing of the outer core was done at temperatures ranging between 150-400° F. for times ranging from 1-30 minutes. After molding, the dual cores were spherically ground to approximately 1.554″ prior to testing.

Table 3 and 4 give details of recipe of inner and outer cores. Components from these recipes were mixed in an internal mixer. Optionally, additional mixing was done using a two roll mill.

Compression of the outer core is measured by first making a full size core separately, measuring its compression, and then molding two halves around the inner core to complete the dual core. Compression differential describes the difference between the outer core compression (as molded independently) and inner core compression. A higher compression differential is more susceptible to crack durability upon impact.

TABLE 3 Inner core recipe Components % wt Polybutadiene rubber 69.2 Polyisoprene rubber 0.0 Zinc diacrylate 14.8 Zinc oxide 12.2 Zinc stearate 2.1 Peroxide initiator 1.0 Zinc pentachlorothiophenol 0.6 Color 0.1 Barium sulfate 0.0 clay 0.0 clay masterbatch 0.0 Properties Compression 0.221

TABLE 4 Outer recipe of dual core Formula 2- Formula 3- ODA silane modified modified Formula 1 clay clay Components % wt % wt % wt Polybutadiene rubber 62.5 62.2 61.9 Polyisoprene rubber 0 0 0 Zinc diacrylate 19.9 19.8 19.7 Zinc oxide 6.3 6.2 6.2 Zinc stearate 3.8 3.7 3.7 Peroxide initiator 0.5 0.5 0.5 Zinc pentachlorothiophenol 0.6 0.6 0.6 Color 0.1 0.1 0.1 Barium sulfate 6.4 6.4 6.4 Clay 0.0 0.5 1.0 Clay masterbatch 0.0 0.0 0.0 Properties of outer core Compression 69.6 70.7 69.5 COR (coefficient of 0.797 0.797 0.798 restitution) Properties of dual core built from inner and outer core Compression 48.7 49.1 46.9 COR (coefficient of 0.796 0.795 0.793 restitution @ 125 fps) Durability score or mean 23 49 52 time to fail MTTF (number of shots after which ball starts to crack/fail)

Compression is measured by applying a 200 pound load to the core and measuring its deflection, in inches. Compression=180−(deflection*1000)

Durability Testing of Dual Cores

Cores were shot at 175 fps in a pneumatic testing machine (PTM). For each formula mentioned in Table 4, 12 cores were tested. Number of shots after which each core cracked was recorded for each core, and the cracked core was removed from the remainder of the test. The data was reported using a Weibull plot, and the mean time to fail was reported as shown in Table 4. As seen in FIG. 25, clay modified cores endured more shots before failure compared to cores with no clay. It is reasonable to assume that the durability of a golf ball having a dual core of this design will also experience a dramatic increase in crack durability based on this improvement to the dual core. It's reasonable to assume that the addition of clay in the inner core could provide a durability enhancement to the overall golf ball, but this study only focused on the outer core.

Clay in Surlyn Mantle

Surlyn (polyethylene based ionomers from DuPont) polymers were extruded along with clay in appropriate amounts as shown in Table 5. These extruded pellets were then used for injection molding mantle on dual cores. In this study, both layers of the dual core did not contain clay in order to assess the improvement isolated to the mantle. The dual cores were all made at the same time and were spherically ground to 1.542″ before injection molding the 5 different mantle layers compositions. The mantles were molded and then spherically ground to 1.614″ to produce a consistent thickness of roughly 0.036″.

Durability Testing of Mantles

Mantles were then shot at 175 fps in a pneumatic testing machine (PTM). For each formula mentioned in Table 5, 12 mantles were tested. Number of shots after which each mantle cracked was recorded and the cracked mantle was removed from the remainder of the test. The data was reported using a Weibull plot, and the mean time to fail was reported as shown in Table 5 and plotted in FIG. 26. Results show that the durability of clay based mantles almost doubled with incorporation of clay and reached a maximum at 1% clay loading. It's also noted that the clay had a negligible effect on the COR of the mantle.

TABLE 5 Mantle recipe Control Formula Formula Formula Formula Description mantle 1 2 3 4 Surlyn 1 (%) 50.00 49.75 49.50 49.25 49.00 Surlyn 2 (%) 50.00 49.75 49.50 49.25 49.00 Clay (%) 0.00 0.50 1.00 1.50 2.00 Properties of mantles Compression 65.7 65.2 64.1 66.5 64.3 COR (coefficient of 0.796 0.795 0.794 0.795 0.791 restitution @ 125 fps) Durability score or 17 27 35 30 24 mean time to fail MTTF (number of shots after which ball starts to crack/fail)

Compression is measured by applying a 200 pound load to the core and measuring its deflection, in inches. Compression=180−(deflection*1000).

Novelty of this process: Durability of the dual core with a high compression differential is greatly enhanced by incorporation of clay in outer core. The clay reinforcement to the outer core helps resist the high stresses experienced by the core when struck at high club speeds. The addition of clay to the core recipe is very simple and can be dispersed into the polybutadiene mixture during two roll milling process. Optionally, clay can be introduced as a masterbatch in polyisoprene, making its dispersion into polybutadiene rubber much easier and dust free.

Dual Core

As our experiment has shown, incorporating clay into the outer core recipe reinforces the strength of the outer core and provides greater crack durability protection in the design of a dual core golf ball, which is more susceptible to crack durability failures if the outer core is much firmer than the soft inner core.

In general, this is applicable when the inner core is softer than the outer core. More specifically, when the inner core has more than 0.200″ deflection under a 200 lb load, and the dual core is 40 compression or greater.

This is particularly crucial if the ball is a 4-piece construction with a single mantle layer with thickness less than 0.050″, or more specifically thinner than 0.040″, with 0.036″ being the target in this study.

Mantle

Incorporating clay into the mantle composition is another means by which we can improve the durability of the dual core, multi-layer golf ball, specifically of the 4-piece design since a single mantle layer alone is protecting the core.

The clay mantle is particularly crucial if the single mantle layer has a thickness less than 0.050″, or more specifically thinner than 0.040″, with 0.036″ being the target in this study.

The clay incorporation can be dry-blended at the injection molding machine, but also specifically done via extrusion compounding prior to injection molding (as done in this study). Whichever method is chosen, durability of golf balls can be greatly enhanced by the incorporation of clay into either the core or mantle layers.

FIGS. 1, 3, 4 and 5 illustrate a five piece golf ball 10 comprising an inner core 12 a, an outer core 12 b, an inner mantle 14 a, an outer mantle 14 b, and a cover 16, wherein the cover layer 16 is composed of a thermoplastic polyurethane and has a Shore A hardness less than 90. The inner core 12 a comprises polybutadiene mixture comprising 0.4 to 2.5 weight percent of a clay material.

FIG. 5A illustrates a five piece golf ball 10 comprising an inner core 12 a, an intermediate core 12 b, an outer core 12 c, a mantle 14, and a cover 16, wherein the cover layer 16 is composed of a thermoplastic polyurethane. The intermediate core 12 b comprises polybutadiene mixture comprising 0.4 to 2.5 weight percent of a CLAY material.

FIGS. 8 and 9 illustrate a six piece golf ball 10 comprising an inner core 12 a, an intermediate core 12 b, an outer core 12 c, an inner mantle 14 a, an outer mantle 14 b, and a cover 16, wherein the cover layer 16 is composed of a thermoplastic polyurethane. The inner core 12 a comprises polybutadiene mixture comprising 0.4 to 2.5 weight percent of a clay material.

FIG. 10 illustrates a four piece golf ball comprising a dual core, a boundary layer and a cover. The outer core comprises polybutadiene mixture comprising 0.4 to 2.5 weight percent of a clay material.

FIG. 11 illustrates a three piece golf ball comprising a core, a boundary layer and a cover. The core comprises polybutadiene mixture comprising 0.4 to 2.5 weight percent of a clay material.

FIGS. 12 and 13 illustrate a two piece golf ball 20 with a core 25 and a cover 30. The core comprises polybutadiene mixture comprising 0.4 to 2.5 weight percent of a clay material.

FIGS. 14 and 15 illustrate a three-piece golf ball 5 comprising a core 10, a mantle layer 14 and a cover 16 with dimples 18, wherein the mantle layer comprises 0.4 to 2.5 weight percent of a clay material, and at least one ionomer material.

FIG. 16 illustrates a dual core three piece golf ball 35 comprising an inner core 30, and outer core 32 and a cover 34, wherein the mantle layer comprises 0.4 to 2.5 weight percent of a clay material, and at least one ionomer material.

FIG. 17 illustrates a three piece golf ball 45 comprising a core 40, a mantle layer 42 and a cover 44, wherein the mantle layer comprises 0.4 to 2.5 weight percent of a clay material, and at least one ionomer material.

FIG. 18 illustrates a dual core four piece golf ball 55 comprising an inner core 50, an outer core 52, a mantle layer 54 and a cover 56, wherein the mantle layer comprises 0.4 to 2.5 weight percent of a clay material, and at least one ionomer material.

FIG. 19 illustrates a four piece golf ball 65 comprising a core 60, an inner mantle 62, an outer mantle 64 and a cover 66, wherein the inner mantle layer comprises 0.4 to 2.5 weight percent of a clay material, and at least one ionomer material.

The mantle component is preferably composed of the inner mantle layer and the outer mantle layer. The mantle component preferably has a thickness ranging from 0.05 inch to 0.15 inch, and more preferably from 0.06 inch to 0.08 inch. The outer mantle layer is preferably composed of a blend of ionomer materials. One preferred embodiment comprises SURLYN 9150 material, SURLYN 8940 material, a SURLYN AD1022 material, and a masterbatch. The SURLYN 9150 material is preferably present in an amount ranging from 20 to 45 weight percent of the cover, and more preferably 30 to 40 weight percent. The SURLYN 8945 is preferably present in an amount ranging from 15 to 35 weight percent of the cover, more preferably 20 to 30 weight percent, and most preferably 26 weight percent. The SURLYN 9945 is preferably present in an amount ranging from 30 to 50 weight percent of the cover, more preferably 35 to 45 weight percent, and most preferably 41 weight percent. The SURLYN 8940 is preferably present in an amount ranging from 5 to 15 weight percent of the cover, more preferably 7 to 12 weight percent, and most preferably 10 weight percent.

SURLYN 8320, from DuPont, is a very-low modulus ethylene/methacrylic acid copolymer with partial neutralization of the acid groups with sodium ions. SURLYN 8945, also from DuPont, is a high acid ethylene/methacrylic acid copolymer with partial neutralization of the acid groups with sodium ions. SURLYN 9945, also from DuPont, is a high acid ethylene/methacrylic acid copolymer with partial neutralization of the acid groups with zinc ions. SURLYN 8940, also from DuPont, is an ethylene/methacrylic acid copolymer with partial neutralization of the acid groups with sodium ions.

The inner mantle layer is preferably composed of a blend of ionomers, preferably comprising a terpolymer and at least two high acid (greater than 18 weight percent) ionomers neutralized with sodium, zinc, magnesium, or other metal ions. The material for the inner mantle layer preferably has a Shore D plaque hardness ranging preferably from 35 to 77, more preferably from 36 to 44, a most preferably approximately 40. The thickness of the outer mantle layer preferably ranges from 0.025 inch to 0.050 inch, and is more preferably approximately 0.037 inch. The mass of an insert including the dual core and the inner mantle layer preferably ranges from 32 grams to 40 grams, more preferably from 34 to 38 grams, and is most preferably approximately 36 grams. The inner mantle layer is alternatively composed of a HPF material available from DuPont. Alternatively, the inner mantle layer 14 b is composed of a material such as disclosed in Kennedy, III et al., U.S. Pat. No. 7,361,101 for a Golf Ball And Thermoplastic Material, which is hereby incorporated by reference in its entirety.

The outer mantle layer is preferably composed of a blend of ionomers, preferably comprising at least two high acid (greater than 18 weight percent) ionomers neutralized with sodium, zinc, or other metal ions. The blend of ionomers also preferably includes a masterbatch. The material of the outer mantle layer preferably has a Shore D plaque hardness ranging preferably from 55 to 75, more preferably from 65 to 71, and most preferably approximately 67. The thickness of the outer mantle layer preferably ranges from 0.025 inch to 0.040 inch, and is more preferably approximately 0.030 inch. The mass of the entire insert including the core, the inner mantle layer and the outer mantle layer preferably ranges from 38 grams to 43 grams, more preferably from 39 to 41 grams, and is most preferably approximately 41 grams.

In an alternative embodiment, the inner mantle layer is preferably composed of a blend of ionomers, preferably comprising at least two high acid (greater than 18 weight percent) ionomers neutralized with sodium, zinc, or other metal ions. The blend of ionomers also preferably includes a masterbatch. In this embodiment, the material of the inner mantle layer has a Shore D plaque hardness ranging preferably from 55 to 75, more preferably from 65 to 71, and most preferably approximately 67. The thickness of the outer mantle layer preferably ranges from 0.025 inch to 0.040 inch, and is more preferably approximately 0.030 inch. Also in this embodiment, the outer mantle layer 14 b is composed of a blend of ionomers, preferably comprising a terpolymer and at least two high acid (greater than 18 weight percent) ionomers neutralized with sodium, zinc, magnesium, or other metal ions. In this embodiment, the material for the outer mantle layer 14 b preferably has a Shore D plaque hardness ranging preferably from 35 to 77, more preferably from 36 to 44, a most preferably approximately 40. The thickness of the outer mantle layer preferably ranges from 0.025 inch to 0.100 inch, and more preferably ranges from 0.070 inch to 0.090 inch.

In yet another embodiment wherein the inner mantle layer is thicker than the outer mantle layer and the outer mantle layer is harder than the inner mantle layer, the inner mantle layer is composed of a blend of ionomers, preferably comprising a terpolymer and at least two high acid (greater than 18 weight percent) ionomers neutralized with sodium, zinc, magnesium, or other metal ions. In this embodiment, the material for the inner mantle layer has a Shore D plaque hardness ranging preferably from 30 to 77, more preferably from 30 to 50, and most preferably approximately 40. In this embodiment, the material for the outer mantle layer has a Shore D plaque hardness ranging preferably from 40 to 77, more preferably from 50 to 71, and most preferably approximately 67. In this embodiment, the thickness of the inner mantle layer preferably ranges from 0.030 inch to 0.090 inch, and the thickness of the outer mantle layer ranges from 0.025 inch to 0.070 inch.

Preferably the inner core has a diameter ranging from 0.75 inch to 1.20 inches, more preferably from 0.85 inch to 1.05 inch, and most preferably approximately 0.95 inch. Preferably the inner core 12 a has a Shore D hardness ranging from 20 to 50, more preferably from 25 to 40, and most preferably approximately 35. Preferably the inner core has a mass ranging from 5 grams to 15 grams, 7 grams to 10 grams and most preferably approximately 8 grams.

Preferably the outer core has a diameter ranging from 1.25 inch to 1.55 inches, more preferably from 1.40 inch to 1.5 inch, and most preferably approximately 1.5 inch. Preferably the outer core has a Shore D surface hardness ranging from 40 to 65, more preferably from 50 to 60, and most preferably approximately 56. Preferably the outer core is formed from a polybutadiene, zinc diacrylate, zinc oxide, zinc stearate, a peptizer and peroxide. Preferably the combined inner core and outer core have a mass ranging from 25 grams to 35 grams, 30 grams to 34 grams and most preferably approximately 32 grams.

Preferably the inner core has a deflection of at least 0.230 inch under a load of 220 pounds, and the core has a deflection of at least 0.080 inch under a load of 200 pounds. As shown in FIGS. 6 and 7, a mass 50 is loaded onto an inner core and a core. As shown in FIGS. 6 and 7, the mass is 100 kilograms, approximately 220 pounds. Under a load of 100 kilograms, the inner core preferably has a deflection from 0.230 inch to 0.300 inch. Under a load of 100 kilograms, preferably the core has a deflection of 0.08 inch to 0.150 inch. Alternatively, the load is 200 pounds (approximately 90 kilograms), and the deflection of the core 12 is at least 0.080 inch. Further, a compressive deformation from a beginning load of 10 kilograms to an ending load of 130 kilograms for the inner core ranges from 4 millimeters to 7 millimeters and more preferably from 5 millimeters to 6.5 millimeters. The dual core deflection differential allows for low spin off the tee to provide greater distance, and high spin on approach shots.

In an alternative embodiment of the golf ball shown in FIG. 5A, the golf ball 10 comprises an inner core 12 a, an intermediate core 12 b, an outer core 12 b, a mantle 14 and a cover 16. The golf ball 10 preferably has a diameter of at least 1.68 inches, a mass ranging from 45 grams to 47 grams, a COR of at least 0.79, a deformation under a 100 kilogram loading of at least 0.07 mm.

In one embodiment, the golf ball comprises a core, a mantle layer and a cover layer. The core comprises an inner core sphere, an intermediate core layer and an outer core layer. The intermediate core layer is composed of a highly neutralized ionomer and has a Shore D hardness less than 40. The outer core layer is composed of a highly neutralized ionomer and has a Shore D hardness less than 45. A thickness of the intermediate core layer is greater than a thickness of the outer core layer. The mantle layer is disposed over the core, comprises an ionomer material and has a Shore D hardness greater than 55. The cover layer is disposed over the mantle layer comprises a thermoplastic polyurethane material and has a Shore A hardness less than 100. The golf ball has a diameter of at least 1.68 inches. The mantle layer is harder than the outer core layer, the outer core layer is harder than the intermediate core layer, the intermediate core layer is harder than the inner core sphere, and the cover layer is softer than the mantle layer.

In another embodiment, shown in FIGS. 8 and 9, the golf ball 10 has a multi-layer core and multi-layer mantle. The golf ball includes a core, a mantle component and a cover layer. The core comprises an inner core sphere, an intermediate core layer and an outer core layer. The inner core sphere comprises a TPEE material and has a diameter ranging from 0.875 inch to 1.4 inches. The intermediate core layer is composed of a highly neutralized ionomer and has a Shore D hardness less than 40. The outer core layer is composed of a highly neutralized ionomer and has a Shore D hardness less than 45. A thickness of the intermediate core layer is greater than a thickness of the outer core layer 12 c. The inner mantle layer is disposed over the core, comprises an ionomer material and has a Shore D hardness greater than 55. The outer mantle layer is disposed over the inner mantle layer, comprises an ionomer material and has a Shore D hardness greater than 60. The cover layer is disposed over the mantle component, comprises a thermoplastic polyurethane material and has a Shore A hardness less than 100. The golf ball has a diameter of at least 1.68 inches. The outer mantle layer is harder than the inner mantle layer, the inner mantle layer is harder than the outer core layer, the outer core layer is harder than the intermediate core layer, the intermediate core layer is harder than the inner core sphere, and the cover layer is softer than the outer mantle layer.

In a particularly preferred embodiment of the invention, the golf ball preferably has an aerodynamic pattern such as disclosed in Simonds et al., U.S. Pat. No. 7,419,443 for a Low Volume Cover For A Golf Ball, which is hereby incorporated by reference in its entirety. Alternatively, the golf ball has an aerodynamic pattern such as disclosed in Simonds et al., U.S. Pat. No. 7,338,392 for An Aerodynamic Surface Geometry For A Golf Ball, which is hereby incorporated by reference in its entirety.

Various aspects of the present invention golf balls have been described in terms of certain tests or measuring procedures. These are described in greater detail as follows.

As used herein, “Shore D hardness” of the golf ball layers is measured generally in accordance with ASTM D-2240 type D, except the measurements may be made on the curved surface of a component of the golf ball, rather than on a plaque. If measured on the ball, the measurement will indicate that the measurement was made on the ball. In referring to a hardness of a material of a layer of the golf ball, the measurement will be made on a plaque in accordance with ASTM D-2240. Furthermore, the Shore D hardness of the cover is measured while the cover remains over the mantles and cores. When a hardness measurement is made on the golf ball, the Shore D hardness is preferably measured at a land area of the cover.

As used herein, “Shore A hardness” of a cover is measured generally in accordance with ASTM D-2240 type A, except the measurements may be made on the curved surface of a component of the golf ball, rather than on a plaque. If measured on the ball, the measurement will indicate that the measurement was made on the ball. In referring to a hardness of a material of a layer of the golf ball, the measurement will be made on a plaque in accordance with ASTM D-2240. Furthermore, the Shore A hardness of the cover is measured while the cover remains over the mantles and cores. When a hardness measurement is made on the golf ball, Shore A hardness is preferably measured at a land area of the cover

The resilience or coefficient of restitution (COR) of a golf ball is the constant “e,” which is the ratio of the relative velocity of an elastic sphere after direct impact to that before impact. As a result, the COR (“e”) can vary from 0 to 1, with 1 being equivalent to a perfectly or completely elastic collision and 0 being equivalent to a perfectly or completely inelastic collision.

COR, along with additional factors such as club head speed, club head mass, ball weight, ball size and density, spin rate, angle of trajectory and surface configuration as well as environmental conditions (e.g. temperature, moisture, atmospheric pressure, wind, etc.) generally determine the distance a ball will travel when hit. Along this line, the distance a golf ball will travel under controlled environmental conditions is a function of the speed and mass of the club and size, density and resilience (COR) of the ball and other factors. The initial velocity of the club, the mass of the club and the angle of the ball's departure are essentially provided by the golfer upon striking. Since club head speed, club head mass, the angle of trajectory and environmental conditions are not determinants controllable by golf ball producers and the ball size and weight are set by the U.S.G.A., these are not factors of concern among golf ball manufacturers. The factors or determinants of interest with respect to improved distance are generally the COR and the surface configuration of the ball.

The coefficient of restitution is the ratio of the outgoing velocity to the incoming velocity. In the examples of this application, the coefficient of restitution of a golf ball was measured by propelling a ball horizontally at a speed of 125+/−5 feet per second (fps) and corrected to 125 fps against a generally vertical, hard, flat steel plate and measuring the ball's incoming and outgoing velocity electronically. Speeds were measured with a pair of ballistic screens, which provide a timing pulse when an object passes through them. The screens were separated by 36 inches and are located 25.25 inches and 61.25 inches from the rebound wall. The ball speed was measured by timing the pulses from screen 1 to screen 2 on the way into the rebound wall (as the average speed of the ball over 36 inches), and then the exit speed was timed from screen 2 to screen 1 over the same distance. The rebound wall was tilted 2 degrees from a vertical plane to allow the ball to rebound slightly downward in order to miss the edge of the cannon that fired it. The rebound wall is solid steel.

As indicated above, the incoming speed should be 125±5 fps but corrected to 125 fps. The correlation between COR and forward or incoming speed has been studied and a correction has been made over the ±5 fps range so that the COR is reported as if the ball had an incoming speed of exactly 125.0 fps.

The measurements for deflection, compression, hardness, and the like are preferably performed on a finished golf ball as opposed to performing the measurement on each layer during manufacturing.

Preferably, in a five layer golf ball comprising an inner core, an outer core, an inner mantle layer, an outer mantle layer and a cover, the hardness/compression of layers involve an inner core with the greatest deflection (lowest hardness), an outer core (combined with the inner core) with a deflection less than the inner core, an inner mantle layer with a hardness less than the hardness of the combined outer core and inner core, an outer mantle layer with the hardness layer of the golf ball, and a cover with a hardness less than the hardness of the outer mantle layer. These measurements are preferably made on a finished golf ball that has been torn down for the measurements.

Preferably the inner mantle layer is thicker than the outer mantle layer or the cover layer. The dual core and dual mantle golf ball creates an optimized velocity-initial velocity ratio (Vi/IV), and allows for spin manipulation. The dual core provides for increased core compression differential resulting in a high spin for short game shots and a low spin for driver shots. A discussion of the USGA initial velocity test is disclosed in Yagley et al., U.S. Pat. No. 6,595,872 for a Golf Ball With High Coefficient Of Restitution, which is hereby incorporated by reference in its entirety. Another example is Bartels et al., U.S. Pat. No. 6,648,775 for a Golf Ball With High Coefficient Of Restitution, which is hereby incorporated by reference in its entirety.

From the foregoing it is believed that those skilled in the pertinent art will recognize the meritorious advancement of this invention and will readily understand that while the present invention has been described in association with a preferred embodiment thereof, and other embodiments illustrated in the accompanying drawings, numerous changes, modifications and substitutions of equivalents may be made therein without departing from the spirit and scope of this invention which is intended to be unlimited by the foregoing except as may appear in the following appended claims. Therefore, the embodiments of the invention in which an exclusive property or privilege is claimed are defined in the following appended claims. 

We claim as our invention the following:
 1. A method for forming a core for a golf ball, the method comprising: mixing at least 60 weight percent of a polybutadiene, 10-50 weight percent of zinc diacrylate, 1-30 weight percent of zinc oxide, 1-20 weight percent of zinc stearate, 0.1-10 weight percent of a peroxide initiator, 0-10 weight percent of zinc pentachlorothiophenol, and 0.4 to 2.5 weight percent of an octadecyl amine (ODA) modified clay material; and compression molding a core from the core mixture.
 2. The method according to claim 1 wherein the core has a diameter ranging from 0.70 inch to 1.6 inch.
 3. The method according to claim 1 further comprising forming a cover over the core.
 4. The method according to claim 1 further comprising forming a mantle layer over the core.
 5. The method according to claim 3 wherein the cover is formed of a TPU. 